National Centre for Immunisation Research and Surveillance
of Vaccine Preventable Diseases (NCIRS), University of Sydney, Royal Alexandra
Hospital for ChildrenNCIRS is a collaborating unit of the Australian Institute of Health and Welfare
This report was prepared at the National Centre for Immunisation Research
and Surveillance of Vaccine Preventable Diseases (NCIRS) by: Robert Menzies,
Peter McIntyre, Frank Beard

Executive summary

This report complements the format of the Vaccine Preventable Diseases and
Vaccination Coverage reports produced biannually since 2000 by the National
Centre for Immunisation Research and Surveillance of Vaccine Preventable Diseases
in association with the Australian Institute of Health and Welfare. It integrates
the available sources of routinely collected data relevant to the current status
of vaccine preventable diseases and vaccine coverage in Aboriginal and Torres
Strait Islander people in Australia. It aims to better inform Indigenous communities,
Indigenous health care providers and planners of immunisation services of the
current status and future needs for vaccine prevention in Indigenous people.

The vaccine preventable diseases (VPDs) presented include only those for which
sufficient data are available, with the addition of measles because of its
importance in national programs. Table 1 summarises the main findings, showing
the reported incidence per 100,000 total population in Indigenous and other
(presumed non-Indigenous) people and the ratio of incidence in Indigenous to
other (presumed non-Indigenous) people. The estimates of incidence in Indigenous
people are based on incomplete ascertainment of Indigenous status and can be
considered as minimum estimates. Table 1 illustrates the large burden (incidence)
and relative burden (rate ratio) of almost all VPDs in Indigenous people. When
measured across all age groups in the Indigenous population, pertussis, influenza
and pneumococcal disease have the highest incidence, though the differential
burden, as measured by the rate ratio, is highest for Haemophilus influenzae type
b (Hib) disease and hepatitis A. It is important to note that the Indigenous
population is significantly younger than the non-Indigenous population and
that both the absolute and relative burdens are greatest in the youngest age
groups for most VPDs.

Invasive disease due to Hib has the highest rate ratio. This is because, although
the total number of cases has decreased markedly since vaccination began in
1993, the decline has plateaued in Indigenous children, who now account for
almost 50 per cent of the total cases occurring under the age of five years.
Vaccination for Hib has been very successful, but progress has slowed for Aboriginal
and Torres Strait Islander children. More information is needed on the reasons
for the widening discrepancy between disease rates in Indigenous and other
people, which has also been seen in North America.

The pattern of hepatitis A shows much higher rates of disease notifications
and, importantly, an even greater differential for hospitalisations, in Indigenous
children aged 0–4 years. By the age of 15 years, this discrepancy has largely
disappeared. These data, particularly the high hospitalisation rates in Indigenous
children, and one death in the most recent 3-year period, contradict the assertion
that hepatitis A is always a mild disease in children. In Far North Queensland,
routine hepatitis A vaccination of Indigenous children from 18 months of age
was introduced in 1999 in response to high numbers of outbreaks, reported deaths
and cases of severe disease. The success of that initiative mirrors that in
other high-incidence populations overseas. The Australian Technical Advisory
Group on Immunisation will examine the use of Hepatitis A vaccination for children,
particularly in relation to Indigenous children, in 2004.

The low rates of hepatitis B disease in Indigenous and other children demonstrate
the success of universal childhood immunisation. However, amongst adolescents
and adults the hospitalisation and notification rates in Indigenous people
are much higher, as is the discrepancy between Indigenous people and others.

With respect to influenza, at present vaccination is recommended and funded
through the National Indigenous Pneumococcal and Influenza Immunisation (NIPII)
program for Indigenous adults aged 15–49 years with risk factors, and for all
Indigenous adults aged 50 years or more. However, there are particularly high
rates of hospitalisation for influenza in age groups not currently targeted
for vaccination—Indigenous children aged 0–4 years and adults aged 25 years
or more. Vaccination of children has recently been recommended in the United
States of America and an evaluation of the impact and reach of the NIPII program
is currently under way. Following this, options to further decrease this high
disease burden should be considered.

Similarly, vaccination to prevent invasive pneumococcal disease is funded
nationally for protein-conjugate vaccine for Indigenous children aged 0–2 years
(0–5 years in Central Australia), and for polysaccharide vaccine in adults
aged 15–49 years with risk factors and all Indigenous adults aged 50 years
or more. The data show the highest relative burden of invasive pneumococcal
disease in the age group not targeted for routine vaccination—Indigenous adults
aged 25 years or more.

There has been very little measles infection in Australia in recent years,
in either Indigenous or other people. The successful control of measles and
other vaccine preventable diseases such as diphtheria, poliomyelitis, rubella
and tetanus, underlines the success and importance of universal vaccination
programs to Indigenous health.

Meningococcal disease notifications show disproportionately high rates in
Indigenous children aged 0–4 years. The limited data on serogroups suggest
that serogroup B, for which there is currently no vaccine, is predominant.
While the recently introduced serogroup C vaccine will have significant benefits
for Aboriginal and Torres Strait Islander children, vaccines for serogroup
B are likely to be particularly important in future. However, any new serogroup
B vaccine will need to be effective against a wider range of subtypes than
the vaccine currently being evaluated in New Zealand.

Pertussis is the least successfully controlled vaccine preventable disease
in Australia, of those which have long been a part of the immunisation program.
The overall notification rate of pertussis in Aboriginal and Torres Strait
Islander people is no higher than in other people. However, in the age group
with the most severe symptoms (0–4 years), the notification rate is 1.7 times
higher in Indigenous children and the rate of hospitalisation is relatively
higher in all Indigenous age groups. Vaccination coverage data indicate that
delayed vaccination of Aboriginal and Torres Strait Islander infants may be
an important contributor to this higher rate; this is the next challenge now
that coverage at 24 months appears to be close to that in non-Indigenous children.

Vaccination coverage data are available nationally for Aboriginal and Torres
Strait Islander children from the Australian Childhood Immunisation Register
(ACIR) and the 2001 National Health Survey (NHS). They use different methods
and provide probable upper and lower estimates of true vaccine coverage. The
highest estimates for Indigenous children come from the ACIR: they show that
82 per cent of 1-year-old children recorded as Indigenous are fully vaccinated,
a rate nine per cent below that for other children. By two years of age, coverage
in Indigenous children has increased to 90 per cent, only one per cent lower
than for other children. The lower estimate from the NHS shows coverage for
Indigenous children aged 2–6 years to be between nine per cent and 17 per cent
lower than non-Indigenous children for individual vaccines. For adults, data
are only available from the NHS for those aged 50 years or more. Coverage is
higher in Indigenous compared to non-Indigenous adults for influenza vaccine
for those aged 50–64 years and for pneumococcal vaccine for those aged 50 years
or more. These data show some impact of the NIPII program, as there is no corresponding
funded program for non-Indigenous adults. However, the coverage estimates for
Aboriginal and Torres Strait Islander adults aged 50 or more years of 51 per
cent for influenza and 25 per cent for pneumococcal disease show considerable
room for improvement. Higher vaccination coverage in Aboriginal and Torres
Strait Islander people in remote areas compared to urban areas is also a fairly
consistent finding from the NHS and regional Australian studies. Further investigation
of reasons for this and of effective ways to improve access to and use of services
by Indigenous people in urban areas is needed.

In conclusion, the data presented here demonstrate that vaccination programs
have had a significant impact on the health of Aboriginal and Torres Strait
Islander people. Several areas are highlighted for further development of vaccination
policy recommendations, in particular high rates of preventable hepatitis A
and B, influenza and pneumococcal disease. Areas where more research is needed
include means to more accurately monitor vaccination status, the applicability
of meningococcal serogroup B vaccines when available, and effective ways of
increasing vaccination coverage and timeliness of vaccination. Such issues
need to be considered and implemented in full cooperation with Aboriginal and
Torres Strait Islander people.

* Notifications (New South Wales, Northern Territory, South
Australia and Western Australia only) where the date of onset was between 1
January 2000 and 31 December 2002, except for pneumococcal disease, which is
from 1 January 2001 to 31 December 2002.

† Notifications per 100,000 population (unless otherwise
specified), age standardised to the Australian Bureau of Statistics Australian
estimated population 2001.2

‡ Includes records where Indigenous status was not
stated.

§ Influenza data are hospitalisations (all states and
territories) where the month of separation was between 1 July 1999 and 30 June
2002.

Introduction

Rationale

Aboriginal and Torres Strait Islander people experience a greater burden of
both communicable and non-communicable diseases compared to the non-Indigenous
population.1 Specific information on vaccination coverage and vaccine
preventable diseases (VPDs) in Aboriginal and Torres Strait Islander people
has been limited, with most published data coming from studies in certain regions
or occasional jurisdictional reports. While national data on other Aboriginal
and Torres Strait Islander health issues have been published utilising existing
administrative data collections,2 this report is the first comprehensive
descriptive analysis of vaccination coverage and vaccine preventable diseases
in Aboriginal and Torres Strait Islander people at the national level. The
report and its rationale have the support of the National Aboriginal Community
Controlled Health Organisation (NACCHO).

Social and economic context

The relationship between socioeconomic status and health is well documented.
A gradient is observable with lower rates of death and most illnesses as socioeconomic
position improves.3 Aboriginal and Torres Strait Islander people
are disadvantaged in terms of most socioeconomic indices (income, education,
employment, housing) compared to other Australians.2 In particular,
the disproportionate exposure to overcrowded living conditions and inadequate
essential infrastructure which Aboriginal and Torres Strait Islander people
experience is known to facilitate the spread of many infectious diseases.2

Demographic context

The Aboriginal and Torres Strait Islander population has a significantly younger
age profile than the Australian population as a whole. Comparisons between
Indigenous and other populations must take age into consideration, either through
age standardisation or stratification by age group.2

Approach

This report presents data on notifications of VPDs and on hospitalisations
and deaths coded as being related to VPDs for the years 1999 to 2002. The completeness
of identification of Aboriginal and Torres Strait Islander people varies between
Australian jurisdictions. In accordance with previous practice,4 the
data for notifications, hospitalisations and deaths are presented in different
combinations of states and territories, as outlined below in the methods section.

Methods

Vaccine preventable diseases data

Three sources of routinely collected data were used for this report. Notification
data were obtained from the National Notifiable Diseases Surveillance System
(NNDSS), hospitalisation data from the Australian Institute of Health and Welfare
(AIHW) National Hospital Morbidity Database, and mortality data from the AIHW
Mortality Database.

Notifications

The NNDSS database includes information about cases of VPDs reported by laboratories
and health workers to state and territory authorities under public health legislation.
State and territory notification criteria were based on the National Health
and Medical Research Council (NHMRC) surveillance case definitions5 in
most jurisdictions. The case definitions presented for each disease in the
results section are those of the NHMRC5 with the exception of pneumococcal
disease, which is taken from Roche, et al.6 New standard
national surveillance case definitions have recently been developed and were
adopted in some jurisdictions during the period covered by this report. However,
any changes in case definitions are unlikely to have a significant impact on
the notification rates presented.

Notifications with an onset between 1 January 2000 and 31 December 2002 were
analysed for this report. The variables extracted for analysis were: disease,
date of disease onset, age at onset, Indigenous status and state or territory
where the notification originated. Following an assessment of completeness
of the Indigenous status field (see below), notifications were included from
New South Wales, the Northern Territory, South Australia and Western Australia.
Detailed data are presented for Haemophilus influenzae type b (Hib)
disease, hepatitis A, acute hepatitis B, measles, meningococcal disease, pertussis,
and pneumococcal disease. Notification data are not presented for VPDs with
few or no notifications in the period (diphtheria, mumps, polio, rubella, tetanus),
or for varicella, for which a vaccine was not widely used during this period.
Summary data for these are provided in Appendix 1. Data are not provided for
influenza notifications due to the low level of completeness of the Indigenous
status field.

Hospitalisations

The AIHW National Hospital Morbidity Database receives administrative, demographic
and clinical information about patients admitted to public and private hospitals
in Australia. Data are received by financial year of hospital separation. The
three most recent years for which data were available (1999/00, 2000/01 and
2001/02) were examined. Data for 2001/02 are provisional because, at the time
of publication, New South Wales data were under revision. The variables extracted
for analysis were: date of separation, age at admission, state or territory
of hospitalisation, Indigenous status and diagnoses. Diagnoses included principal
and other with up to 31 diagnoses for each admission, coded using the International
Statistical Classification of Diseases and Related Health Problems, 10th Revision,
Australian Modification, 1st Edition (ICD–10–AM). Eligible separations were
those with the code of interest listed in any diagnosis field except for hepatitis
B, where only principal diagnoses were included. Detailed data are presented
for hepatitis A, acute hepatitis B, influenza and pneumonia, measles, meningococcal
disease, pertussis, and pneumococcal disease. Separation data are not presented
in the results section for those VPDs with few or no separations during the
period (diphtheria, mumps, polio, rubella, tetanus), with no specific ICD10
code (Hib disease), or for which a vaccine was not widely used during this
period (varicella). Summary data for these diseases are provided in Appendix
1.

Deaths

Death data were obtained from the AIHW Mortality Database. These data are
supplied annually to the AIHW by the Australian Bureau of Statistics (ABS).
Analysis was by year of registration for the three most recent years for which
data were available (2000 to 2002). The variables extracted were: age, state
or territory of registration, Indigenous status, and underlying cause of death,
coded using the International Classification of Disease, 10th Revision (ICD–10).
Deaths where the disease of interest was recorded as the underlying cause are
used in this report. Following previous practice,2 mortality data
for those jurisdictions considered to have the most complete coverage of Aboriginal
and Torres Strait Islander deaths (Queensland, South Australia, Western Australia
and the Northern Territory) were combined. For diseases included in the results
section, numbers of deaths are presented by age group where appropriate, and
as summary data. For those VPDs not included in the results section (diphtheria,
mumps, polio, rubella, tetanus and varicella), summary data are provided in
Appendix 1.

Calculations

Incidence rates in Aboriginal and Torres Strait Islander people were calculated
using ABS estimates of Indigenous populations as at mid-2001.1 Incidence
rates for other (presumed non-Indigenous) persons were calculated using as
the denominator the total ABS estimated resident population as at mid-2001,
minus the relevant Indigenous population. Rates for all ages combined were
age standardised to the ABS Australian population estimates for 2001,1 for
both those categorised as Indigenous and other. Rate ratios for Indigenous
versus other persons were calculated for each disease, with age-specific rate
ratios where appropriate. All rates are presented as average annual rates per
100,000 total population or population by age group, as appropriate.

Vaccination coverage data

Data on coverage for various vaccines at the national level were provided
by the Health Insurance Commission (from the Australian Childhood Immunisation
Register [ACIR]) and the Australian Bureau of Statistics (from the 2001 National
Health Survey).

The ACIR is administered by the Health Insurance Commission (HIC) for the
Australian Government Department of Health and Ageing, and records the vaccination
service details of children aged less than seven years from data supplied by
vaccine providers. Vaccination coverage estimates derived from ACIR data have
been reported in Communicable Diseases Intelligence since early 1998.
A complete description of the method for calculating coverage estimates by
age cohorts is given elsewhere.7 National data on coverage in children
recorded as Aboriginal and Torres Strait Islander have not been published previously.

The 2001 National Health Survey included a supplementary survey of 3,198 Aboriginal
and Torres Strait Islander adults and children in order to improve the precision
of estimates of Indigenous people. The sample covered all areas of Australia,
including sparsely settled areas. When combined with the main survey, the total
Indigenous sample size was 3,681.8 This survey provided national
data on the immunisation status of Aboriginal and Torres Strait Islander people
for the first time in Australia. This report includes more detailed tabulations
not previously published. Immunisation status was collected by face-to-face
interview for both adults and children. Respondents were asked to consult written
records if available. Vaccinations were regarded as given if at least a date
of vaccination was supplied. Children were regarded as vaccinated appropriately
for age if the vaccine was administered up to one month after the recommended
age. Thus, data from the National Health Survey are not directly comparable
with the ACIR due to differences in both the methods of data collection and
calculation of vaccination status.

Data quality and notes on interpreting data

As a consequence of differences in data quality and availability, the time
periods and states and territories included in this report differ between data
collections. Comparing data from the different collections is therefore problematic
and should take account of the various factors outlined below.

Indigenous identification

The quality of Indigenous health statistics depends on both the accuracy of
Indigenous population estimates and the level of completeness and accuracy
of reporting achieved in the collection of Indigenous status for the condition
of interest.2 Considerable work has been done in recent years on
assessing and improving the quality of Indigenous statistics in national and
state and territory administrative data collections.2 More work
is needed to improve the quality of the data, as large variations in quality
exist between data collections, between States, and over time. For this report,
data and analyses chosen for inclusion are in most instances similar to previous
publications on those data collections.2 This is not the case where
there have been changes in data quality since the last publication, or no previous
assessment has been carried out, as specified below.

Notification data

Indigenous identification

The proportion of notifications lacking identification of Indigenous status
were analysed by state, year and disease. Adequate levels of completeness of
Indigenous status identification between 2000 and 2002 were defined as at least
60 per cent for a substantial majority of the diseases analysed. This level
of completeness was achieved for New South Wales, South Australia, Western
Australia and the Northern Territory. After first establishing that the notification
incidence estimates were not dominated by any one of these four States for
all diseases of interest (data not shown), estimates are presented for the
four jurisdictions combined. Although a previous presentation of notifications
for the period 1998–20004 excluded New South Wales, data completeness
for this State between 2000 and 2002 was found to be comparable to that of
South Australia and Western Australia. As a high proportion of influenza notifications
lacked identification of Indigenous status in all states and territories, other
than the Northern Territory, influenza was excluded from further analysis.

Overall, estimated Indigenous notification rates can be considered underestimates,
due to the incomplete recording of Indigenous status.

Other issues

A major consideration in interpreting notification data is that they represent
only a proportion of the total cases occurring in the community. This proportion
is usually unknown and may vary between diseases, with infections diagnosed
by a laboratory test more likely to be notified. Data accuracy may also vary
between states and territories, due to the use of different case definitions
for surveillance and varying reporting requirements by medical practitioners,
laboratories and hospitals. In addition, data accuracy may change over time
as new diagnostic tests are introduced or surveillance practices change.

Hospitalisation data

Indigenous identification

Although the overall proportion of hospitalisations lacking identification
of Indigenous status was low (less than 5%) from 1999/00 to 2001/02, variability
in completeness and in accuracy of identification have been previously documented.4,9 The
proportion of Aboriginal and Torres Strait Islander people correctly identified
in hospital records has varied between 44 per cent and 100 per cent in studies
conducted in various jurisdictions since 1997.9 Following previous
practice,2 hospital separations are presented for all jurisdictions
combined. Indigenous hospitalisation rates can also be considered underestimates
due to the incomplete identification of Aboriginal and Torres Strait Islander
people.

Other issues

There are limitations associated with the use of ICD–10–AM codes to identify
cases. Hospital coding errors have been reported to occur more commonly for
diseases that the coder was less familiar with and for admissions with multiple
diagnoses.10 Assignation of codes is based on information in medical
records, as recorded by clinicians, without strict case definitions. This is
in contrast with the more stringent case definitions used for notification
data. Indigenous hospitalisations where the code of interest was in any diagnosis
field were included, and the relative importance of these cannot be gauged.
For acute hepatitis B, cases were only included where the code of interest
was the principal diagnosis, as previous studies have found a substantially
lower proportion of principal diagnoses compared to other diseases.11,12

It should also be noted that the hospitalisation database contains a record
for each admission, which means that there are separate records for each readmission
or inter-hospital transfer. This is unlikely to have a major impact on the
numbers reported for most diseases reviewed, as they are acute illnesses, but
may inflate the numbers of hospitalisations where inter-hospital transfer is
more frequent, either because of remote residence or the severity of the illness.

The accuracy of reporting Indigenous status on deaths has been previously
evaluated by comparing the reported number with an expected, or predicted,
number of Indigenous deaths.2 Reporting was found to be acceptable
for deaths in 1997–1999 in Queensland, South Australia, Western Australia and
the Northern Territory. Following previous practice,2 reported deaths
from these four States only have been presented in this report. These combined
rates may still underestimate Indigenous death rates due to under-reporting.

Other issues

Mortality data were analysed by year of registration rather than by year of
death. Approximately six per cent of deaths in a particular calendar year are
registered in the subsequent year, mostly deaths in the previous December.
Issues associated with the accuracy of the ICD codes used for hospital separations
may also apply to mortality data.

Vaccination coverage data

Indigenous identification

The completeness of reporting of Indigenous status on the ACIR was analysed
by comparing the number of children recorded as Aboriginal or Torres Strait
Islander on the ACIR with ABS 2001 Census data. Indigenous status is currently
either not routinely reported or not transferred to the ACIR from the Australian
Capital Territory, Queensland and Tasmania, so these jurisdictions were not
included in this report. For New South Wales, the Northern Territory, South
Australia, Victoria and Western Australia, 61 per cent of the estimated cohort
of Aboriginal or Torres Strait Islander children aged 12–18 months and 65 per
cent of the estimated cohort aged 24–30 months were recorded as Aboriginal
or Torres Strait Islander on the ACIR. The accuracy of the information recorded
in the Indigenous status field was assessed by comparison of Hib vaccines received,
adapting a method developed by Hull, et al.13 Until May 2000,
different Hib vaccines were recommended for Indigenous (Hib vaccine conjugated
to outer membrane protein of Neisseria meningitidis, Pedvax) and non-Indigenous
(Hib vaccine conjugated to a mutant diphtheria toxin, HibTiter) children. Children
born between 1 January and 30 April 2000 and recorded on the ACIR as receiving
a Hib vaccine and being Aboriginal or Torres Strait Islander were 27 times
more likely to have received a dose of Pedvax. Children recorded as receiving
a dose of Pedvax were nine times more likely to be recorded as Aboriginal or
Torres Strait Islander than children who received other Hib vaccines. These
data suggest an acceptable level of correlation between the recording of Indigenous
status and the receipt of a vaccine recommended only for Aboriginal and Torres
Strait Islander children.

Other issues

General limitations of data available from the ACIR must be considered when
used to estimate vaccination coverage. A study conducted in 2001 found that
the ACIR underestimated overall Australian immunisation coverage by 2.7 per
cent at 12 months of age and five per cent at 24 months.14 However,
for Aboriginal and Torres Strait Islander children these estimates may not
be valid, as there is the issue of both under-reporting of vaccinations given
to the ACIR and incomplete identification of Indigenous children. This means
that ACIR coverage estimates could overestimate or underestimate coverage,
depending on whether those children not identified as Aboriginal and Torres
Strait Islander have higher or lower than average vaccination coverage. The
ACIR holds records only for children up to seven years of age. Coverage is
calculated only for children registered on Medicare; however, current data
show that by the age of 12 months practically all Australian children have
been registered with Medicare (personal communication, Kathi Williams, Health
Insurance Commission, April 2004).

Indigenous population estimates

Estimation of the size and age composition of the Aboriginal and Torres Strait
Islander population is difficult. Increases in census counts of Aboriginal
and Torres Strait Islander people between 1966 and 1996 are far greater than
can be explained by simple demographic factors (births minus deaths).15 Other
factors thought to be important include changes in: the propensity to identify
as Indigenous in the Census; the proportion of children with only one Aboriginal
and Torres Strait Islander parent identified as Indigenous; and Census enumeration
procedures.4,15

In this report, Australian Bureau of Statistics estimates of Aboriginal and
Torres Strait Islander population figures, based on 2001 Census data,1 are
used.

Results

Haemophilus influenzae type b disease

Haemophilus influenzae is a fastidious Gram-negative bacterium, which
occurs in both encapsulated and unencapsulated forms. Before Hib vaccines became
available, one encapsulated serotype, type b (Hib), caused at least 95 per
cent of invasive infections due to H. influenzae (those associated
with isolation of the organism from a normally sterile site) in children.16,17 The
most common manifestation of invasive Hib disease was meningitis, with children
aged less than 18 months most at risk.17–19 Aboriginal children
had a particularly high risk of Hib meningitis, with a recorded incidence among
children living in Central Australia among the highest in the world and an
earlier age of onset than non-Indigenous children.20 Survivors of
Hib meningitis commonly had neurological sequelae such as deafness and intellectual
impairment. Epiglottitis, a potentially fatal inflammation of the epiglottis
obstructing breathing, was the other major category of infection, but was rare
in Aboriginal and Torres Strait Islander children.20 Less common
manifestations of invasive Hib disease include a range of focal infections
(cellulitis, septic arthritis, pneumonia, pericarditis, osteomyelitis) and
septicaemia without focus.

Haemophilus influenzae type b

Case definitions

Notifications

(a) A clinically compatible illness (meningitis, epiglottitis, cellulitis,
septic arthritis, osteomyelitis, pneumonia, pericarditis or septicaemia)
and either:
isolation of Haemophilus influenzae type b from blood or
detection of Hib antigen (in a clinically compatible case) or
detection of Gram-negative bacteria of characteristic appearance where
the organism fails to grow in a clinical case

or

b) A confident diagnosis of epiglottitis by direct vision, laryngoscopy
or X-ray.

Hospitalisations and deaths

Hospitalisations and deaths were not analysed as there are no ICD–10–AM/ICD–10
codes which specify Hib as a causative organism, as opposed to Haemophilus
influenzae (type unspecified).

In 2000–2002, there were a total of 47 notifications of invasive Hib disease
in the jurisdictions with adequate data, 24 in children 0–4 years, of whom
11 (46%) were identified as Aboriginal and Torres Strait Islander (Table 2).
The notification rate of 10 per 100,000 in Aboriginal and Torres Strait Islander
children under five years of age gave a rate ratio of 15 for this age group,
compared to four in persons five years and over. Cases in Aboriginal and Torres
Strait Islander children were not wholly or predominantly reported from any
one jurisdiction.

A similar number of notifications were received for persons 0–4 years and
five years of age and over. Among 0–4 year olds, there was a striking difference
in the annual notification rates for Aboriginal and Torres Strait Islander
(10 per 100,000) and other children (0.7 per 100,000).

* New South Wales, Northern Territory, South Australia and
Western Australia only, where the date of onset was between 1 January 2000
and 31 December 2002.

† Average annual age-specific rate per 100,000 population.

‡ Rates for all ages combined are age standardised to the
ABS Australian population estimates for 2001.1

Comment

The Hib immunisation program in Australia commenced in April 1993, with catch-up
immunisation for children up to five years of age from July 1993. Until June
2000, Aboriginal and Torres Strait Islander children were scheduled to receive
a different Hib vaccine (conjugated to the outer membrane of Neisseria meningitidis type
C, PRP–OMP) than other children who received a vaccine conjugated to a mutant
diphtheria toxin (CRM197). Since June 2000, all Australian children have received
PRP–OMP vaccine.

Following the introduction of Hib vaccination in 1993, children aged up to
15 years and children born since the introduction of the program up to 10 years
of age by July 2003 were eligible to receive it. Indigenous status was poorly
reported in the National Notifiable Diseases Surveillance System until the
late 1990s, but an enhanced surveillance scheme for invasive Hib disease, established
in 1993, included Indigenous status.21 Vaccination has had a striking
impact on the incidence of Hib disease in the age groups targeted by immunisation
programs, among both Indigenous and non-Indigenous children.21 Compared
to an incidence of 35–40 per 100,000 in the general population and up to 280
per 100,000 in Aboriginal and Torres Strait Islander children living in the
Northern Territory,22 notification rates presented in this report
(0.7 and 10.0 respectively in 2000–2002) represent a reduction of almost 98
per cent since vaccination was introduced.

Although the number of cases has decreased markedly, the proportion of total
Hib disease cases occurring in Aboriginal and Torres Strait Islander people
has increased from around seven per cent before 1993 to 15 per cent in 2000.21 This
report shows a further increase in the differential between Aboriginal and
Torres Strait Islander people and others to a rate ratio of 10 overall and
15 among children under five years of age. However, the point estimate for
incidence in Aboriginal and Torres Strait Islander children under five years
of 10.0 per 100,000 compares favourably with that among American Indian children
in 2001–2002.21 A similar pattern of increasing disparity in Hib
disease rates has also been observed between Maori-Pacific Islander children
and other children in New Zealand.23 The available data indicate
that Hib immunisation rates are acceptable in Aboriginal and Torres Strait
Islander children in some geographic areas.13,22 However, the role
of regional variations in immunisation coverage should be examined as a likely
reason for this increasing disparity. Crowded living conditions may also be
a factor, being associated with high levels of Hib colonisation in the nasopharynx.
In the meantime, the experience of similar Indigenous populations in Alaska24 suggests
that continued use of a Hib vaccine which is immunogenic after the first dose
is appropriate in Aboriginal and Torres Strait Islander children.

Infection with the hepatitis A virus (HAV), a picorna virus, produces symptoms
with a wide range from subclinical hepatitis to acute hepatitis with jaundice
and, in the most severe cases, fulminant hepatitis leading to death. The single
most important factor in determining the outcome of HAV infection is age. In
symptomatic adult cases, onset of clinical symptoms is usually abrupt with
fever, anorexia, malaise, nausea and abdominal discomfort followed by jaundice.
In contrast, over 90 per cent of infections acquired before the age of five
years are clinically silent. In adults, the proportion of infected individuals
showing symptoms is thought to be around 90 per cent.25,26

Hepatitis A

Case definitions

Notifications

a) Detection of anti-hepatitis A virus IgM antibody, in the absence
of recent vaccination

or

b) A clinical case of hepatitis (jaundice ± elevated aminotransferase
levels, without a non-infectious cause) and an epidemiological link
to a serologically confirmed case.

Hospitalisations and deaths

The ICD–10–AM/ICD–10 codes B15 (hepatitis A) were
used to identify hospitalisations and deaths.

Distribution
by Indigenous status and age

Of the total of 1,012 notifications of hepatitis A recorded in the relevant
jurisdictions, 113 (11%) were identified as occurring in Aboriginal and Torres
Strait Islander people, as were 82 (6%) of the 1,309 hospitalisations recorded
nationally. The overall rate ratio of cases identified as Indigenous to those
presumed to be non-Indigenous was three for notifications and two for hospitalisations.
Both hospitalisation (16 per 100,000) and notification (37 per 100,000) rates
were highest among children 0–4 years identified as Indigenous, with the absolute
number of cases higher than in other children (Table 3) and rate ratios of
57 and 22 respectively. This excess morbidity falls sharply with age, with
smaller but substantial Indigenous versus other rate ratios among children
5–14 years of age (8 for notifications, 7 for hospitalisations), decreasing
to two or less from the age of 15 years. Figures 1 and 2 illustrate the striking
difference between young children and others when comparing both notifications
and hospitalisations for Indigenous and other people.

Table 3. Hepatitis A notifications, hospitalisations and deaths,
Australia, 1999 to 2002,* by age group and Indigenous status

Age group
(years)

Indigenous status

Notifications
(2000–2002)

Hospitalisations
(July 1999–June 2002)

Deaths
(2000–2002)

n

Rate†

Rate ratio

n

Rate†

Rate ratio

n

0–4

Indigenous

41

37.1

22.2

28

15.5

56.8

1

Non-Indigenous

32

1.7

10

0.3

0

5–14

Indigenous

44

20.2

7.7

16

4.5

7.1

0

Other

105

2.6

49

0.6

0

15–24

Indigenous

13

8.4

2.0

10

4.0

1.9

0

Other

163

4.1

161

2.1

0

25–49

Indigenous

13

4.7

1.1

28

6.3

2.3

0

Other

479

4.3

585

2.8

0

50+

Indigenous

2

2.3

1.6

0

0.0

0.0

0

Other

120

1.4

422

2.5

2

All ages

Indigenous

113

9.1

2.9

82

4.5

2.1

1

Other

899

3.1

1227

2.1

2

* Notifications (New South Wales, Northern Territory, South
Australia and Western Australia only) where the date of onset was between 1
January 2000 and 31 December 2002; hospitalisations (all States) where the
date of separation was between 1 July 1999 and 30 June 2002; deaths (Queensland,
Northern Territory, South Australia, Western Australia) where the date of death
was recorded between 1 January 2000 and 31 December 2002.

† Average annual age-specific rate per 100,000 population.

‡ Includes cases with unknown ages. Rates for all ages combined
are age standardised to the ABS Australian population estimates for 2001.1

Figure 1. Hepatitis A notification rate, selected Australian
States,* 2000 to 2002,† by age group and Indigenous status

* New South Wales, South Australia, Western Australia and
the Northern Territory.

† Notifications where the date of onset was between
1 January 2000 and 31 December 2002.

Figure 2. Hepatitis A hospitalisation rate, Australia, 1999 to 2002,* by
age group and Indigenous status

* Hospitalisations
where the date of separation was between 1 July 1999 and 30 June 2002.

Comment

The data in this report show
a high burden of hepatitis A among Aboriginal and Torres Strait Islander
children, with a progressive decrease in incidence with increasing age. The
high rate ratio for hospitalisations due to hepatitis A in children under
the age of five years is particularly noteworthy, indicating that higher
rates of disease are reflected in significantly higher levels of morbidity
in Aboriginal and Torres Strait Islander children. One death was coded as
due to hepatitis A in an Aboriginal and Torres Strait Islander child in the
reporting period, and other such deaths have been reported recently in North
Queensland.27

The pattern of acquisition
of hepatitis A is known to vary substantially according to living standards.
More advantaged communities have delayed or no exposure to hepatitis A, with
the majority seronegative even in middle age, while communities living in
crowded and/or less hygienic circumstances acquire infection and immunity
to hepatitis A at an early age. In the Northern Territory in 1994, a serosurvey
in rural Aboriginal populations found hepatitis A to be hyperendemic, with
acquisition of the virus predominantly in the first five years of life,28 as
is characteristic of disadvantaged living conditions. It was argued that,
in such circumstances, immunisation is of little benefit and may produce
a cohort whose immunity could subsequently wane.28 Although case-fatality
and hospitalisation rates are low in children, with a high rate of infection
some serious outcomes can be expected. In comparable Indigenous populations
in the United States of America (USA), with similar high infection rates
and age distribution, community-wide hepatitis A immunisation was recommended29 and
has resulted in dramatic reductions in the incidence of hepatitis A.30 The
recommendations have been expanded more recently to include the routine vaccination
of children in areas where the rate of hepatitis A exceeds 20 per 100,000
population.29

In Australia, an immunisation
program for hepatitis A was commenced among children from 18 months of age
in North Queensland in 1999, in response to two deaths in Far North Queensland
Aboriginal and Torres Strait Islander children from fulminant hepatitis A.27 Early
results from this program indicate that despite targeting only Aboriginal
and Torres Strait Islander children, substantial reductions in hepatitis
A across all sectors of the population groups have occurred.31 Currently,
no funded hepatitis A immunisation program exists in Australia outside of
north Queensland. The favourable experience with hepatitis A immunisation
programs in north Queensland, and in high incidence areas of the United States
of America, is in accord with experience in other highly endemic areas.32 The
Australian Technical Advisory Group on Immunisation will examine the use
of hepatitis A vaccination for children, particularly in relation to Indigenous
children, in 2004.

Acute infection with hepatitis
B virus (HBV), a hepadnavirus, may produce a range of conditions from subclinical
hepatitis to acute hepatitis with jaundice and, rarely, fulminant hepatitis.
Only a small proportion of HBV infections are clinically recognised, with
less than 10 per cent of children and 30–50 per cent of adults experiencing
clinical symptoms.33 Onset of illness, when it occurs, is usually
insidious with anorexia, vague abdominal discomfort, nausea and vomiting
and sometimes arthralgia and rash, often progressing to jaundice. The principal
cause of morbidity and mortality from hepatitis B is chronic infection, which
may occur irrespective of symptoms. Chronic infection can lead to cirrhosis
of the liver and hepatocellular carcinoma, usually over a prolonged period.34 The
risk of chronic infection is greatest in those infected as infants, particularly
if infected in the perinatal period. Accordingly, preventive efforts have
been focussed, in both the Indigenous and non-Indigenous community in Australia,
on preventing maternal-infant transmission.

Hepatitis B (acute)

Case definitions

Notifications

People who have a positive hepatitis B surface antigen (HBsAg) and
one of the following:
hepatitis B core antibody (Anti-HBc) IgM

ICD–10–AM code B16 (acute hepatitis B) was used to identify
hospitalisations.
As in previous reports,12 hospitalisations were included only where the
relevant ICD code was the principal diagnosis (which was in 30% of all
hospitalisations which included acute hepatitis B). This is a much lower
proportion than for the other diseases but similar to previous analyses
of hepatitis B hospitalisations.33

Of the total of 526 notifications
of acute hepatitis B recorded in the relevant jurisdictions, 57 (11%) were
identified as occurring in Aboriginal and Torres Strait Islander people,
as were 30 (6%) of the 463 hospitalisations recorded nationally. The overall
rate ratio for cases identified as Indigenous compared to those presumed
to be non-Indigenous was four for both notifications and hospitalisations
(Table 4). In contrast to hepatitis A, no notified or hospitalised cases
of hepatitis B were recorded as Indigenous among children 0–4 years. Notification
rates for acute hepatitis B then increased progressively among Aboriginal
and Torres Strait Islander people, reaching a peak among 15–24 year olds
and continuing to show a higher incidence in absolute and relative terms
compared with other groups at all ages, maximal in those over 50 years (Figure
3). This was also reflected in hospitalisations (Figure 4). The highest notification
rates per 100,000 were seen in both Indigenous and other populations in the
15–24 years (14 versus 4) and 25–49 years (10 versus 2) age groups. The highest
hospitalisation rates per 100,000 were seen in 25–49 year old cases identified
as Indigenous (5 per 100,000) with a rate ratio of four. Of the 10 deaths
recorded, two were in persons identified as Indigenous, both aged 25–49 years.

Table 4.
Acute hepatitis B notifications, hospitalisations and deaths, Australia,
1999 to 2002,* by age group and Indigenous status

Age
group
(years)

Indigenous
status

Notifications
(2000–2002)

Hospitalisations
(July 1999–June 2002)

Deaths
(2000–2002)

n

Rate†

Rate
ratio

n

Rate†

Rate
ratio

n

0–4

Indigenous

0

0.0

0.0

0

0.0

0.0

0

Other

3

0.2

1

0.0

0

5–14

Indigenous

3

1.4

5.5

1

0.3

3.1

0

Other

10

0.2

7

0.1

0

15–24

Indigenous

22

14.1

3.5

3

1.2

1.0

0

Other

162

4.1

98

1.3

2

25–49

Indigenous

29

10.4

4.6

22

4.9

4.2

2

Other

249

2.3

250

1.2

1

50+

Indigenous

3

3.4

6.8

4

2.8

6.0

0

Other

43

0.5

77

0.5

5

All
ages

Indigenous

57

7.2

4.4

30

2.8

3.7

2

Other

469

1.6

433

0.8

8

* Notifications
(New South Wales, Northern Territory, South Australia and Western Australia
only) where the date of onset was between 1 January 2000 and 31 December
2002; hospitalisations (all States) where the date of separation was between
1 July 1999 and 30 June 2002; deaths (Northern Territory, South Australia,
Queensland, Western Australia) where the date of death was recorded between
1 January 2000 and 31 December 2002.

† Average
annual age-specific rate per 100,000 population.

‡ Includes
cases with unknown ages. Rates for all ages combined are age standardised
to the ABS Australian population estimates for 2001.1

Figure 3. Acute hepatitis B notification rate, selected Australian States,* 2000 to
2002,† by age group and Indigenous status

* New South
Wales, South Australia, Western Australia and the Northern Territory.

† Notifications
where the date of onset was between 1 January 2000 and 31 December 2002.

* Hospitalisations
where the date of separation was between 1 July 1999 and 30 June 2002.

Comment

The mortality and morbidity
from hepatitis B among Aboriginal and Torres Strait Islander people has been
recognised for at least two decades and led to childhood hepatitis B vaccination
programs being introduced in the Northern Territory in the 1980s.33 Aboriginal
and Torres Strait Islander newborns were also targeted for risk-based hepatitis
B immunisation programs, along with children born to hepatitis B surface
antigen positive mothers or parents born in countries with a high incidence
of hepatitis B from this time. In contrast to hepatitis A, the greatest differential
morbidity from hepatitis B is in the age groups over 15 and particularly
over 25 years. This is consistent with some impact from immunisation programs,
as the oldest cohorts of children targeted for immunisation would now be
around 15 years of age.

The highest incidence of
acute hepatitis B and the greatest differential between Indigenous and other
hepatitis B incidence has always been in adolescents and young adults,33 and
remains so in these data. Hepatitis B immunisation could be considered for
adolescents and young adults, including prison populations, until birth cohorts
eligible for hepatitis B vaccine reach adulthood. While providing information
on acute disease, these data do not reflect the significant chronic disease
burden from hepatitis B for Aboriginal and Torres Strait Islander people,
including liver cancer.

Influenza is an acute respiratory
illness caused by influenza type A or B viruses. Onset of clinical symptoms
is typically abrupt with fever, cough, myalgia and prostration. Outbreaks
of variable severity occur almost every winter in Australia and are associated
with significant morbidity and mortality, particularly in the elderly and
chronically ill. The most common complication of influenza is pneumonia.
It is generally believed that hospitalisations and deaths coded as influenza
significantly underestimate disease burden, with excess all-cause pneumonia
and influenza combined, during the influenza season, being a better indicator
of true disease burden.35

Influenza and pneumonia

Case definitions

Hospitalisations and deaths

The ICD–10–AM/ICD–10 codes J10 and J11 (influenza)
were used to identify hospitalisations and deaths from influenza. The
ICD–10–AM/ICD10 codes J10 to J18 were used to identify
hospitalisations and deaths from influenza and all-cause pneumonia
combined.

Distribution
by Indigenous status and age

Rates of hospitalisation
were higher in all Indigenous age groups for both influenza and influenza
and pneumonia combined, with the highest rate ratio (7) for influenza and
pneumonia combined in the 25–49 years age group (Table 5). While rates of
influenza and pneumonia combined are substantially higher than for influenza
alone, the pattern of distribution by age group is very similar (Figures
5 and 6, allowing for different scales). The rate ratio for deaths was highest
in those aged 25–49 (28), 15–24 (15) and 0–4 years (17).

Table 5.
Influenza and pneumonia hospitalisations and deaths, Australia 2000 to 2002,*
by age group and Indigenous status

Age group
(years)

Indigenous status

Hospitalisations
(July 1999–June 2002)

Deaths
(2000–2002)

Influenza

Influenza and pneumonia

Influenza

Influenza and pneumonia

n

Rate†

Rate ratio

n

Rate†

Rate ratio

n

n

Rate†

Rate ratio

0–4

Indigenous

230

127.3

2.5

5,682

3146

4.3

0

18

10.0

17.4

Other

1,877

51.2

26,885

733

3

21

0.6

5–14

Indigenous

45

12.7

1.5

1,304

367

2.7

0

1

0.3

10.9

Other

643

8.3

10,471

135

0

2

0.0

15–24

Indigenous

53

21.0

1.8

1,056

419

4.4

0

1

0.4

15.3

Other

883

11.4

7,383

96

1

2

0.0

25–49

Indigenous

149

33.4

2.7

5,416

1212

7.4

0

34

7.6

27.8

Other

2,591

12.2

34,536

163

3

58

0.3

50+

Indigenous

117

83.1

3.7

3,997

2,838

2.3

2

76

54.0

2.6

Other

3,725

22.5

204,601

1,236

54

3,486

21.0

All ages‡

Indigenous

594

49.3

2.9

17,455

1580

3.2

2

130

19.1

3.1

Other

9,719

17.1

283,876

495

61

3,569

6.2

* Hospitalisations
(all States) where the date of separation was between 1 July 1999 and 30
June 2002; deaths (Queensland, Northern Territory, South Australia and Western
Australia) where the date of death was recorded between 1 January 2000 and
31 December 2002.

† Average
annual age-specific rate per 100,000 population.

‡ Includes
cases with unknown ages. Rates for all ages combined are age standardised
to the Australian Bureau of Statistics Australian population estimates for
2001.1

Figure 5.
Hospitalisation rate for influenza, Australia, 1999 to 2002,* by age group
and Indigenous status

* Hospitalisations
where the date of separation was between 1 July 1999 and 30 June 2002.

Figure 6.
Hospitalisation rate for influenza and all pneumonia combined, Australia,
1999 to 2002,* by age group and Indigenous status

* Hospitalisations
where the date of separation was between 1 July 1999 and 30 June 2002.

Comment

The relatively high morbidity
from influenza and related conditions in older Aboriginal and Torres Strait
Islander adults led to a specific program for influenza and pneumococcal
vaccine being funded nationally for Indigenous adults over 50 years in 1999
and those aged 15–49 years with risk factors.36 This is in contrast
to the non-Indigenous population, for whom influenza vaccine is funded only
from age 65 years and pneumococcal vaccine is funded only in Victoria for
this age group. Young children also experience high morbidity from influenza,
with minimal estimates, such as those in this report based on hospital coding
data, still showing a high incidence of hospitalisation under five years
of age. Although only five per cent of deaths coded as attributable to influenza
nationally were in persons under five years and none in Aboriginal and Torres
Strait Islander children, there was a twofold differential in the influenza
hospitalisation rate between Indigenous and other children.

The importance of young children,
both in terms of their own high morbidity from influenza and their role in
transmission of influenza to adults, has been increasingly appreciated in
recent years.37 This has led to a recommendation in the United
States of America that all children between six and 24 months of age receive
influenza vaccine.38 This recommendation is particularly pertinent
to Aboriginal and Torres Strait Islander children in Australia, where influenza
may contribute significantly to overall respiratory morbidity in children
and adults they are in contact with, especially in crowded living conditions.
Evaluation of the reach and impact of the current National Indigenous Pneumococcal
and Influenza Immunisation (NIPII) program in adults and the potential role
of influenza immunisation in children or universally in at least some communities
of Aboriginal and Torres Strait Islander people is needed. Subsequently,
consideration of the role of influenza immunisation in young Aboriginal and
Torres Strait Islander children would be appropriate.

Measles is an acute and highly
communicable disease caused by a morbillivirus. The clinical picture includes
a prodromal fever, rash, conjunctivitis, coryza, cough and Koplik spots on
the buccal mucosa. Complications include otitis media, pneumonia and encephalitis.
Subacute sclerosing panencephalitis occurs very rarely as a late sequel.35

Measles

Case definitions

Notifications

An illness characterised by all the following features:
a generalised maculopapular rash lasting three or more days, and
a fever (at least 38º C if measured), and
cough or coryza or conjunctivitis or Koplik spots

or

Demonstration of measles specific IgM antibody

or

A fourfold or greater rise in measles antibody titre between acute
and convalescent phase sera obtained at least two weeks apart, with
tests preferably conducted at the same laboratory

or

Isolation of measles virus from a clinical specimen

or

A clinically compatible case epidemiologically related to another
case.

Hospitalisations and deaths

The ICD–10–AM/ICD–10 code B05 (measles) was used
to identify hospitalisations and deaths. Subacute sclerosing panencephalitis
was not included in these analyses.

Distribution
by Indigenous status

Only 113 notifications and
172 hospitalisations recorded as being associated with measles were seen
in the relevant jurisdictions or Australia respectively during the reporting
period examined. Of these, only 3 (2.6%) notifications and 2 (1.1%) hospitalisations
were recorded as Indigenous, with equivalent incidence in Indigenous and
other persons (Table 6). No deaths were recorded in the reporting period.

Table 6.
Measles notifications, hospitalisations and deaths, Australia, 1999 to 2002,*
by age group and Indigenous status

Age
group
(years)

Indigenous
status

Notifications
(2000–2002)

Hospitalisations
(July 1999–June 2002)

Deaths
(2000–2002)

n

Rate†

Rate
ratio

n

Rate†

Rate
ratio

n

All
ages

Indigenous

3

0.2

0.6

2

0.1

0.4

0

Other

110

0.4

170

0.3

0

* Notifications
(New South Wales, Northern Territory, South Australia and Western Australia
only) where the date of onset was between 1January 2000 and 31 December 2002;
hospitalisations (all States) where the date of separation was between 1
July 1999 and 30 June 2002; deaths (Queensland, Northern Territory, South
Australia and Western Australia) where the date of death was recorded between
1 January 2000 and 31 December 2002.

† Average
annual rate per 100,000 population.

‡ Includes
cases with unknown ages. Rates are age standardised to the ABS Australian
population estimates for 2001.1

Comment

Two significant milestones
in measles control occurred in Australia in 1998; the Measles Control Campaign
(MCC), involving catch-up immunisation of 1.3 million children aged 5–12
years, and the moving of the second dose of measles-mumps-rubella (MMR) vaccine
from 12 to four years.39 This reporting period follows the MCC
and is in a period when transmission of measles in Australia is believed
to have been largely limited to introduction of virus from overseas, with
limited local transmission among age-groups with high levels of immunity
from immunisation (under 15 years) or past infection (over 35 years).40 Measles
outbreaks have been almost entirely confined to children who were unimmunised,
either because of young age or refusal to vaccinate, and to young adults
aged 18–30 years.41

Measles was associated with
high levels of morbidity among Aboriginal and Torres Strait Islander children
in the past, prompting the Northern Territory to introduce immunisation at
nine months of age, with a subsequent booster, for Aboriginal children.42 This
program ended in the Northern Territory in 199843 and no excess
morbidity from measles is evident in this or other Australian jurisdictions.
The successful control of measles in Aboriginal and Torres Strait Islander
people is a reflection of the almost total success of immunisation in preventing
measles transmission, in contrast to other VPDs such as pertussis or Hib
disease. It illustrates the importance of universal programs, across all
relevant age groups in the population, in disease prevention in both Indigenous
and non-Indigenous people.

Clinical manifestations of
meningococcal disease include meningitis, meningococcaemia without meningitis
(which varies in presentation from fulminant to chronic) and septic arthritis.

Meningococcal disease

Case definitions

Notifications

Isolation of Neisseria meningitidis from a normally sterile
site

or

Detection of meningococcal antigen in joints, blood or cerebrospinal
fluid

or

Detection of Gram-negative intracellular diplococci in blood or cerebrospinal
fluid.

Hospitalisations and deaths

The ICD–10–AM/ICD–10 code A39 (meningococcal infection)
was used to identify hospitalisations and deaths.

Distribution
by Indigenous status and age

Notification and hospitalisation
rates (per 100,000 population) showed a progressive decrease with increasing
age in both Indigenous and other persons (Table 7). The notification rate
fell from a peak of 51 in the 0–4 age group for Indigenous and 15 in other
children, to eight and four respectively in 5–14 year olds, with the lowest
rates in 25–49 year olds in both groups (Figure 7). Overall, the rate ratio
for notifications comparing Indigenous versus others was two, but was close
to unity among 15–49 year olds, differing only at the extremes of age. The
pattern for hospitalisations was similar, with again the lowest hospitalisation
rates among Aboriginal and Torres Strait Islander people aged 15–49 years,
although one of the five Indigenous deaths recorded occurred in this age
band (Figure 8).

Serogroup
distribution by Indigenous status and age

Serogroup data were not available
for hospitalisations and were missing for 63 per cent of Indigenous and 45
per cent of other notifications, so conclusions about serogroup distribution
are subject to significant limitations. In notifications where serogroup
was known, a higher proportion of cases identified as Indigenous were serogroup
B (73% compared to 59% in other cases) with a lower proportion due to serogroup
C (27% compared to 38%).

Table 7.
Meningococcal disease notifications, hospitalisations and deaths, Australia,
1999 to 2002,* by age group and Indigenous status

Age
group
(years)

Indigenous
status

Notifications
(2000–2002)

Hospitalisations
(July 1999–June 2002)

Deaths
(2000–2002)

n

Rate†

Rate
ratio

n

Rate†

Rate
ratio

n

0–4

Indigenous

56

50.7

3.5

76

42.1

2.1

4

Other

280

14.6

731

20.4

12

5–14

Indigenous

18

8.3

2.1

29

8.2

1.7

0

Other

158

3.9

364

4.8

3

15–24

Indigenous

8

5.1

0.7

7

2.8

0.3

1

Other

273

6.9

756

9.5

5

25–49

Indigenous

4

1.4

1.0

5

1.1

0.7

0

Other

162

1.5

349

1.6

8

50+

Indigenous

4

4.5

4.3

4

2.8

1.9

0

Other

91

1.1

240

1.5

5

All
ages

Indigenous

92

7.2

2.1

121

5.5

1.3

5

Other

975

3.4

2,440

4.3

33

* Notifications
(New South Wales, Northern Territory, South Australia and Western Australia
only) where the date of onset was between 1 January 2000 and 31 December
2002; hospitalisations (all States) where the date of separation was between
1 July 1999 and 30 June 2002; deaths (Queensland, Northern Territory, South
Australia and Western Australia) where the date of death was recorded between
1 January 2000 and 31 December 2002.

† Average
annual age-specific rate per 100,000 population.

‡ Includes
cases with unknown ages. Rates for all ages combined are age standardised
to the ABS Australian population estimates for 2001.1

Figure 7.
Meningococcal disease notification rate, selected Australian States*, 2000
to 2002,† by age group and Indigenous status

* New South
Wales, South Australia, Western Australia and the Northern Territory.

† Notifications
where the date of onset was between 1 January 2000 and 31 December 2002.

Figure 8.
Meningococcal disease hospitalisation rate, Australia, 1999 to 2002,* by
age group and Indigenous status

* Hospitalisations
where the date of separation was between 1 July 1999 and 30 June 2002.

Comment

The available data on meningococcal
disease were limited by lack of serogroup information, which is important
given the introduction of conjugate meningococcal C vaccine into the Australian
Standard Vaccination Schedule (ASVS) for all children 1–19 years in 2002.
The overall pattern of invasive meningococcal disease shown here indicates
a secondary peak in notifications and hospitalisations among 15–24 year olds
presumed non-Indigenous persons not evident in Indigenous people. In both
groups, the age-specific incidence is highest among 0–4 year olds, being
about tenfold higher in Indigenous 0–4 year olds (51) than in 15–24 year
olds (5) and twofold higher in the comparable (presumed) non-Indigenous age
groups. In keeping with this, the greatest differential disease burden was
in 0–4 year olds, with a rate ratio of Indigenous to other notifications
of 3.5. Indigenous deaths accounted for 13 per cent of the total, similar
to the proportion of notifications (9%), but four of five these deaths (80%)
occurred in 0–4 year olds compared with 12 (36%) of other deaths.

Historically, the incidence
of meningococcal disease has been disproportionately higher among Aboriginal
and Torres Strait Islander Australians, with well-recorded outbreaks in Central
Australia44 and north-west Queensland due to type A and type C
disease.45 The current pattern appears, from the limited data
available, to be more one of serogroup B disease in the youngest children,
similar to that seen in Maori and Pacific Islander children in New Zealand,46 in
whom living conditions have been shown to be an important disease risk factor.47 Vaccines
protecting against serogroup B disease will be an important consideration
for Aboriginal and Torres Strait Islander children in the future, but will
need to be effective against a wider range of serogroup B subtypes than the
vaccine currently being evaluated in New Zealand.48

Pertussis (whooping cough)
is an acute illness, caused by the Bordetella pertussis bacterium,
involving the respiratory tract. The typical illness begins with an irritating
cough that gradually becomes paroxysmal and lasts for 1–2 months or longer.
Paroxysms are characterised by repeated violent coughs, followed by a characteristic
crowing or high-pitched inspiratory whoop. Infants less than six months old,
adolescents and adults often have fewer classical symptoms without paroxysms
or whoop.49

Pertussis

Case definitions

Notifications

Isolation of Bordetella pertussis from a clinical specimen

or

Elevated B. pertussis-specific IgA in serum or the detection of B.
pertussis antigen in a nasopharyngeal specimen using immunofluorescence
with history of a clinically compatible illness

or

An illness lasting two weeks or more with one of the following:
paroxysms of coughing, or
inspiratory whoop without other apparent causes, or
post-tussive vomiting.

or

An illness characterised by a cough lasting at least two weeks in
a patient who is epidemiologically linked to a laboratory confirmed
case.

Hospitalisations and deaths

The ICD–10–AM/ICD–10 code A37 (whooping cough) was
used to identify hospitalisations and deaths.

Distribution
by Indigenous status and age

The age-specific pattern
of notifications among Indigenous and other people differed substantially,
even though the overall notification rates were almost identical at 42 and
47 respectively per 100,000. For Aboriginal and Torres Strait Islander people,
there was an almost twofold higher notification rate among 0–4 year olds
and over 50 year olds, with relatively lower notification rates in those
aged 5–49 years (Figure 9). In contrast, there was a relative excess of hospitalisations
for Aboriginal and Torres Strait Islander people in all age groups, except
25–49 year olds, with an overall rate ratio of two (Figure 10). Hospitalisations
were predominantly in those aged 0–4 years, (130/150, 87%) of those recorded
as Indigenous and (957/1478, 62%) of other children.

In view of the large differential
in rates for 0–4 year olds and relatively large case numbers, incidence in
the under one year age group was also examined. The notification rate (per
100,000 population) was substantially higher in Indigenous (308) compared
to other infants (120), with a rate ratio twice that seen in the 0–4 years
age group. However, while hospitalisation rates under 12 months were more
than threefold higher than the overall 0–4 years age group at 196 per 100,000
Indigenous and 89 per 100,000 other, there was no difference between the
rate ratios at 0–11 months and 12–59 months of age (Table 8). Seven deaths
were recorded as due to pertussis during the reporting period, five in presumed
non-Indigenous children under 12 months of age and two in presumed non-Indigenous
adults over 50 years.

Table 8.
Pertussis notifications, hospitalisations and deaths, Australia, 1999 to
2002,* by age group and Indigenous status

Age
group
(years)

Indigenous
status

Notifications
(2000–2002)

Hospitalisations
(July 1999–June 2002)

Deaths
(2000–2002)

n

Rate†

Rate
ratio

n

Rate†

Rate
ratio

n

0–4

Indigenous

99

89.7

1.7

130

72.0

2.8

0

Other

1,038

54.3

957

26.1

5

5–14

Indigenous

133

61.1

0.6

10

2.8

1.3

0

Other

4,372

108.6

167

2.2

0

15–24

Indigenous

58

37.3

0.8

4

1.6

3.1

0

Other

1,798

44.9

40

0.5

0

25–49

Indigenous

73

26.3

0.7

3

0.7

0.9

0

Other

4,130

37.3

150

0.7

0

50+

Indigenous

35

39.6

1.6

3

2.1

2.2

0

Other

2,083

24.1

164

1.0

2

All
ages

Indigenous

408

41.8

0.9

150

6.2

2.4

0

Other

1,3528

46.9

1,478

2.6

7

* Notifications
(New South Wales, Northern Territory, South Australia and Western Australia
only) where the date of onset was between 1 January 2000 and 31 December
2002; hospitalisations (all States) where the date of separation was between
1 July 1999 and 30 June 2002; deaths (Queensland, Northern Territory, South
Australia and Western Australia) where the date of death was recorded between
1 January 2000 and 31 December 2002.

† Average
annual age-specific rate per 100,000 population.

‡ Includes
cases with unknown ages. Rates for all ages combined are age standardised
to the ABS Australian population estimates for 2001.1

Figure 9.
Pertussis notification rate, selected Australian States,* 2000 to 2002,† by
age group and Indigenous status

* New South
Wales, South Australia, Western Australia and the Northern Territory.

† Notifications
where the date of onset was between 1 January 2000 and 31 December 2002.

Figure 10. Pertussis
hospitalisation rate, Australia, 1999 to 2002,* by age group and Indigenous
status

* Hospitalisations
where the date of separation was between 1 July 1999 and 30 June 2002.

Comment

Pertussis is the disease
least well controlled of all the diseases with long-standing, well-established
vaccination programs. It has the highest notification rate for all ages for
the total Australian population12 and, with the exception of influenza,
meningococcal and pneumococcal diseases and varicella, the highest hospitalisation
rates. The data in this report are the first to examine this in relation
to Indigenous status nationally, although data have been reported previously
from the Northern Territory.50 Interpretation of the data is complex,
because of the marked differences between age groups in immunisation history
and disease severity as measured by hospitalisation and deaths. Despite this,
the relatively large number of cases compared with other VPDs among Aboriginal
and Torres Strait Islander people allows some interesting conclusions.

First, the greatest relative
excess of pertussis is in 0–4 year olds, most marked in infants under 12
months of age and in hospitalisations. Second, the relatively lower notification
rates and rate ratios seen between five and 49 years of age are not reflected
in hospitalisation data. This could be artefactual, due to diagnostic practice
or lack of access to laboratory facilities in more remote areas, or a real
phenomenon, perhaps related to greater exposure to pertussis and more long-lasting
immunity in Aboriginal and Torres Strait Islander adults and older children.
Even in presumed non-Indigenous children, the age group 5–14 years is a diverse
one in relation to vaccination history, as an additional dose of pertussis
vaccine was included in the ASVS from 1994. More detailed analysis shows
a progressive cohort effect among this age group, shown by high rates in
the oldest members of the cohort and low rates among the younger ones, similar
that of 1–4 year olds.51 From the beginning of 2004, an additional
dose of a pertussis-containing vaccine will replace diphtheria-tetanus vaccine
for all Australian 15–17 year olds.52 It will be important to
monitor trends following this change according to Indigenous status to fully
examine its impact.

Pneumococcal disease is caused
by the bacterium Streptococcus pneumoniae (pneumococcus). Pneumococci
are frequently isolated from the upper respiratory tract and can spread directly
from the nasopharynx to cause infection in other parts of the respiratory
tract (otitis media, sinusitis, pneumonia) or enter the bloodstream. Manifestations
include meningitis, pneumonia and infection at a number of less common sites,
as well as septicaemia without focal infection. Invasive pneumococcal disease
(IPD) is defined as a sterile site isolate of Streptococcus pneumoniae,
usually from blood. In the absence of a sterile site isolate, a presumptive
diagnosis of pneumococcal pneumonia may be based on a sputum isolate of Streptococcus
pneumoniae and/or clinical features such as the chest X-ray appearance
and prompt response to antibiotic therapy. Invasive pneumococcal disease
has been notifiable in Queensland and the Northern Territory since 1997.
From January 2001, invasive pneumococcal disease became notifiable Australia-wide.

Pneumococcal disease

Case definitions

The ICD–10–AM codes used to identify hospitalisations
were: G00.1, pneumococcal meningitis; A40.3, pneumococcal septicaemia
(together considered to be a proxy for invasive pneumococcal disease);
and J13, pneumococcal pneumonia.

Deaths

ICD–10 codes G00.1 and A40.3 were used (together considered
to be a proxy for invasive pneumococcal disease) to select deaths from
IPD.

Distribution
by Indigenous status and age

Notification and hospitalisation
rates for invasive pneumococal disease were higher for all Indigenous age
groups with an overall Indigenous: other rate ratio of five for notifications
and hospitalisations (Table 9). Rates per 100,000 population were highest
in both Indigenous and other populations for the 0–4 years age group (notifications
87 versus 49; hospitalisations 45 versus 26) and 50+ years age group (notifications
59 versus 14; hospitalisations 29 versus 8). Importantly, the incidence of
IPD began to increase significantly in the 25–49 years Indigenous age group
to an incidence of 48 per 100,000 compared with four per 100,000 in other
persons. The incidence rate ratios remained significantly higher at approximately
three even for the lowest incidence age group of 5–24 years, with the notification
rate among Aboriginal and Torres Strait Islander young people remaining 10
per 100,000, equivalent to that seen among other people over 50 years of
age (Figure 11). The age distribution was similar for notifications of IPD
and for hospitalisations. For hospitalisations coded as pneumococcal pneumonia,
without septicaemia or meningitis, a similar pattern was also found, but
was accentuated among those over 50 years and showed a much lower hospitalisation
rate for 0–4 year olds (Figures 12 and 13). Death was recorded as due to
IPD in 21 cases in the reporting period, 24 per cent of whom were Aboriginal
and Torres Strait Islander. In 0–4 year olds, 2/8 deaths (25%) were in Aboriginal
and Torres Strait Islander children, 2/3 (67%) among 5–49 year olds and 1/10
(10%) of deaths occurring in over 50 year olds.

Table 9.
Invasive pneumococcal disease notifications, hospitalisations and deaths,
Australia, 1999 to 2002*, by age group and Indigenous status

Age
group
(years)

Indigenous
status

Notifications†
(2001–2002)

Hospitalisations
(July 1999–June 2002)

Deaths
(2000–2002)

n

Rate

Rate
ratio

n

Rate

Rate
ratio

n

0–4

Indigenous

64

87.0

1.8

81

44.8

1.7

2

Other

620

48.6

944

25.7

6

5–14

Indigenous

15

10.3

2.7

24

6.8

4.0

0

Other

102

3.8

130

1.7

1

15–24

Indigenous

10

9.6

3.7

15

6.0

8.2

1

Other

70

2.6

58

0.8

0

25–49

Indigenous

89

48.1

11.9

108

24.2

13.4

1

Other

297

4.0

384

1.8

0

50+

Indigenous

35

59.4

4.3

41

29.1

3.7

1

Other

800

13.9

1290

7.8

9

All
ages||

Indigenous

214

44.7

4.5

269

22.0

4.5

5

Other

1,926

9.9

2,806

4.9

16

* Notifications
(New South Wales, Northern Territory, South Australia and Western Australia
only) where the date of onset was between 1 January 2001 and 31 December
2002; hospitalisations (all States) where the month of separation was between
1 July 1999 and 30 June 2002; deaths (Queensland, Northern Territory, South
Australia and Western Australia) where the date of death was recorded between
1 January 2000 and 31 December 2002.

† Notifications
are presented for two years only as invasive pneumococcal disease became
nationally notifiable in January 2001. Completeness of the Indigenous status
data field was suboptimal for New South Wales data in 2001.

‡ Using
hospitalisations for pneumococcal meningitis and pneumococcal septicaemia
as a proxy for invasive pneumococcal disease

§ Average
annual age-specific rate per 100,000 population.

|| Includes
cases with unknown ages. Rates for all ages combined are age standardised
to the ABS Australian population estimates for 2001.1

Figure 11. Invasive
pneumococcal disease notification rate, selected Australian States,* 2001
to 2002,† by age group and Indigenous status

* New South Wales, South Australia, Western Australia and
the Northern Territory.

† Notifications where the date of onset was between
1 January 2001 and 31 December 2002.

Figure 12. Hospitalisation rate for pneumococcal meningitis
and septicaemia, Australia, 1999 to 2002,* by age group and Indigenous status

* Hospitalisations where the date of separation was between
1 July 1999 and 30 June 2001.

Figure 13. Hospitalisation rate for pneumococcal pneumonia
(not coded as meningitis or septicaemia), Australia, 1999 to 2002,* by age
group and Indigenous status

* Hospitalisations where the date of separation was between
1 July 1999 and 30 June 2002

Comment

Invasive pneumococcal disease
is well recognised as causing a significant disease burden among Aboriginal
and Torres Strait Islander people, especially in Northern and Central Australia.53,54 The
data presented in this report reinforce the importance of IPD as a priority
for vaccine prevention in Aboriginal and Torres Strait Islander people of
all ages. In particular, the data indicate that IPD has an incidence in younger
Aboriginal and Torres Strait Islander adults (25–49 years) almost as high
as in the age group currently targeted for pneumococcal vaccine, those over
50 years. It should be noted that the pattern of age-specific incidence seen
for IPD is almost identical to that seen for influenza and pneumonia.

Currently, IPD is targeted
for vaccine prevention among Aboriginal and Torres Strait Islander children
0–2 years of age, except in Central Australia and adjacent areas, where the
conjugate pneumococcal vaccine program is extended to five years. From the
age of 15 years, only adults with risk factors for IPD are included in recommendations
or funding for polysaccharide vaccine, with the exception of the Northern
Territory, where all Aboriginal and Torres Strait Islander adults aged 15
years or more are eligible. From the age of 50 years, funded vaccine is provided
for all Aboriginal and Torres Strait Islander adults.

It is too early for definitive
data to be available on the impact of the conjugate vaccine program among
Aboriginal and Torres Strait Islander infants, but available data indicate
that vaccine coverage is sub-optimal, particularly in the south-east of Australia.
For adults, data from the program in North Queensland indicate that, in a
setting where high coverage with pneumococcal polysaccharide vaccine has
been achieved, substantial disease reductions have been observed.55 However,
recent data from the USA in Navajo populations suggest sub-optimal efficacy
of pneumococcal polysaccharide vaccine, particularly in adults with underlying
medical conditions such as alcoholism.56 Based on the data presented
here on disease rates, and assuming that vaccine effectiveness is adequate,
a universal pneumococcal polysaccharide vaccination program for 25–49 year
old Aboriginal and Torres Strait Islanders may be justified and should be
further evaluated.

Vaccination
coverage

Australian
Standard Vaccination Schedule 1998 to 2003

The Australian Standard Vaccination
Schedule for children aged 0–6 years changed in the second half of 1998,
in mid 2000 and in January and September 2003. In 1998, the second dose of
measles-mumps-rubella vaccine (previously given at 12–13 years) was moved
to four years. For children born after May 2000, full vaccination at 12 months
of age required immunisation against hepatitis B as well as three doses of
diphtheria-tetanus-pertussis vaccine (DTP) and oral poliomyelitis (OPV) vaccines.
Full immunisation against Haemophilus influenzae type b disease at
12 months required, from 2000, two doses of PRP–OMP (Haemophilus influenzae type
b polysaccharide conjugated to the outer membrane protein of Neisseria
meningitidis) vaccine for all children. The neonatal dose of hepatitis
B vaccine (scheduled for all newborns since May 2000) is not accounted for
in ACIR coverage estimates. In the second year of life, a dose of MMR vaccine
is scheduled at 12 months of age as well as booster doses of DTP (at 18 months)
and Hib vaccine (at 12 months); the 18 month dose of (DTP) was removed in
September 2003. The 7-valent pneumococcal conjugate vaccine (7vPCV) was introduced
for children at high risk of invasive pneumococcal disease (including all
Aboriginal and Torres Strait Islander children) in June 2001. The meningococcal
C conjugate vaccine (MenCCV) was introduced for all children in January 2003.
The current ASVS is shown in Table 10.

Table 10.
The Australian Standard Vaccination Schedule57

Age

Vaccine

Birth

Hepatitis B*

2 months

Hepatitis B*

DTPa

Hib‡

IPV║

7vPCV**

4 months

Hepatitis B*

DTPa

Hib‡

IPV║

7vPCV**

6 months

Hepatitis B*

DTPa

Hib§

IPV║

7vPCV**

12 months

Hepatitis B*

Hib‡

MMR

MenCCV

18 months

VZV¶

23vPPV††

2 years

4 years

DTPa

IPV║

MMR

10–13 years

Hepatitis B†

VZV¶

15–17 years

dTpa

50 years and over

dT

23vPPV‡‡

Influenza (annual)‡‡

65 years and over

23vPPV

Influenza (annual)

Note: Vaccines
currently funded under the National Immunisation Program are shaded in Table
10 above. Vaccines lightly shaded are funded for targeted, at-risk populations
only.

* 4 doses
of hepatitis B vaccine recommended for each child, the timing of doses varies
according to the vaccine formulation used.

† 2
or 3 catch up doses recommended for children not previously immunised.

‡ 3
doses of PRP–OMP recommended for all children.

§ A
4-dose schedule of PRP–T or HbOC may be given to non-Indigenous children
as an alternative.

║ IPV
is recommended but not funded by the National Immunisation Program; OPV is
funded as an alternative.

¶ Only
for children with a negative history of disease or vaccination.

** Recommended
for all children, provided free only to: all Aboriginal and Torres Strait
Islander children aged up to two years, Indigenous children in Central Australia
aged up to five years, non-Indigenous children in Central Australia aged
up to two years, and all children under five years with medical risk factors
that predispose them to high rates or high severity of pneumococcal infection.

Specific recommendations
for Aboriginal or Torres Strait Islander people

There are several differences
between the vaccines recommended for Indigenous and non-Indigenous Australians,
mainly due to differences in disease incidence. The Australian Standard Vaccination
Schedule contains recommendations specifically for Aboriginal and Torres
Strait Islander people for influenza, pneumococcal disease and Hib disease.
There are also additional recommendations for Aboriginal and Torres Strait
Islander people for tuberculosis and hepatitis A vaccines, which are limited
to some geographical regions.

The 23-valent pneumococcal
polysaccharide vaccine is recommended for all Aboriginal and Torres Strait
Islander people aged 50 years and over, and for those aged 15–49 years who
have high-risk underlying conditions. In the Northern Territory, vaccination
is recommended for all Aboriginal and Torres Strait Islanders aged 15 years
or more. A single re-vaccination is generally recommended five years later
(see the Australian Immunisation Handbook 8th edition for more details).57 Annual
influenza vaccination is also recommended for Aboriginal and Torres Strait
Islander adults aged 50 years and over, and for those aged 15 to 49 years
with high-risk underlying conditions. These vaccines are funded under the
National Indigenous Pneumococcal and Influenza Immunisation Program. The
recommendations for non-Indigenous adults differ in that vaccination for
these two diseases is recommended from 65 years of age instead of 50. Influenza
vaccine is provided for non-Indigenous adults aged 65 or more years under
the National Immunisation Program. Pneumococcal vaccine is not publicly funded
for non-Indigenous adults except in Victoria, although it is subsidised on
the Pharmaceutical Benefits Scheme.

The 7-valent pneumococcal
conjugate vaccine is recommended for all children at two, four and six months
of age. It is provided free under the National Immunisation Program for all
Aboriginal and Torres Strait Islander children and for non-Indigenous children
with high risk conditions. Aboriginal and Torres Strait Islander children
living in high incidence areas (Northern Territory, South Australia, Western
Australia, Queensland) should also receive a dose of 23-valent vaccine at
18–24 months. Catch up vaccination is recommended for unvaccinated children
up to five years of age in Central Australia and up to two years of age in
other areas.

PRP-OMP (purified polysaccharide
conjugated to an outer membrane protein carrier) Hib vaccine is immunogenic
at an earlier age and therefore requires fewer doses than other Hib vaccines.
For PRP-OMP vaccine, doses are recommended at two, four and 12 months of
age, while other Hib vaccines require an extra dose at six months. Since
Hib vaccine was first introduced onto the ASVS in 1993, PRP–OMP has been
recommended for Aboriginal and Torres Strait Islander children, due to their
higher risk of disease under six months of age. Other Hib vaccines were recommended
for non-Indigenous children until May 2000. Since then, either PRP–OMP or
PRP–T/HbOC vaccines are recommended for non-Indigenous children.

Since 1999, hepatitis A vaccine
has been provided for all Aboriginal and Torres Strait Islander children
in North Queensland at 18 and 24 months of age. Catch-up vaccination is provided
to children up to six years of age.

Vaccination with BCG (Bacille
Calmette-Guérin) vaccine for tuberculosis is recommended for all Aboriginal
and Torres Strait Islander neonates in high incidence areas.

Vaccination for Japanese
encephalitis virus is recommended for all residents of the outer Islands
of the Torres Strait aged over one year of age, and non-residents staying
at least 30 days during the wet season.

Calculating
vaccination coverage estimates from the ACIR

The methodology for calculating
cohort-based vaccination coverage from the ACIR was described by 0'Brien et
al.7 Using this method, a cohort of children is defined by
date of birth in 3-month groups; the first cohort was born between 1 January
1996 and 31 March 1996. To minimise duplicate records, the cohort includes
only children enrolled with Medicare. The vaccination status of each cohort
is assessed at the two key milestones of 12 months and 24 months of age.
Coverage is measured several months after the due date for completion of
each milestone, to allow for delayed notification to the ACIR. It is assumed
that notification of receipt of a later vaccine dose implies receipt of earlier
doses, even if no earlier vaccination is recorded ('third dose assumption').58

A child is now defined as
'fully vaccinated' at 12 months of age if he or she has received a third
dose of DTPa and poliomyelitis vaccine (oral or inactivated), a second dose
of Hib vaccine (PRP–OMP), and either a second or a third dose of hepatitis
B vaccine. At 24 months of age a child is defined as fully vaccinated if
he or she has received the third dose of DTPa, OPV and Hib, either a third
or fourth dose of hepatitis B and a first dose of MMR. ACIR coverage estimates
have been reported in Communicable Diseases Intelligence since 1998.7 Coverage
estimates for Aboriginal and Torres Strait Islander children are not published
separately except in those jurisdictions where agreement has been reached
with the relevant jurisdictional organisation(s).

The completeness of data
on Indigenous status was assessed by State and Territory. As a result, data
were included only for New South Wales, Northern Territory, South Australia,
Victoria and Western Australia. See Methods for more information.

Vaccination
coverage estimates from the ACIR for Indigenous versus other children

Coverage estimates from the
ACIR for Aboriginal and Torres Strait Islander children and children not
identified as Indigenous aged one and two years are shown in Table 11. For
Aboriginal and Torres Strait Islander children, 82.2 per cent of one year
olds and 90.1 per cent of two year olds were fully immunised. The proportion
fully immunised at 12 months of age was considerably higher for children
not identified as Indigenous (9% higher than Indigenous children) and less
so at two years of age (1% higher).

Coverage at 12 months of
age was lower for Aboriginal and Torres Strait Islander children for each
single vaccine. However, at two years of age, the differences in coverage
for individual vaccines between Indigenous and other children were less marked.
Coverage was higher in Aboriginal and Torres Strait Islander two year olds
for hepatitis B (Indigenous 97.9%, other 95.5%), DTP (Indigenous 96.7%, other
95.7%), OPV (Indigenous 95.3%, other 94.5%) and MMR (Indigenous 94.2%, other
93.1%).

It should be noted, however,
that coverage estimates for Aboriginal and Torres Strait Islander children
include only those who are registered on the ACIR and identified on it as
Indigenous. Children so identified may not be representative of all Aboriginal
and Torres Strait Islander children, and so estimates based on these could
either overestimate or underestimate coverage among young Indigenous children.

Table 11.
Coverage estimates from the Australian Childhood Immunisation Register for
Indigenous and other children 'fully vaccinated' at age 1 and 2 years*

* 3-month
cohorts, age at 30 September 2003, calculated at 31 December 2003. Coverage
assessment date was 12 or 24 months after the last birth date of each cohort.
Includes data from New South Wales, Northern Territory, South Australia,
VIC, Western Australia only.

† Not
included in coverage estimates for that age group.

Calculating
vaccination coverage estimates from the National Health Survey

The methodology for calculating
vaccination coverage estimates in the National Health Survey (NHS) has been
published.8 In contrast to ACIR estimates, NHS estimates for children
are combined for different ages, in this case 2–6 years of age. The NHS was
conducted in 2001, so for this age group, three different schedules have
applied—those of 1996, 1998 and 2000. Some of the schedule changes applied
only to children born after that date, while others applied to all children
below a certain age, depending on the vaccine and dose concerned. The vaccination
status for each child was calculated according to the number of doses received,
compared to the number recommended under the schedule applying to a child
in that age group. An allowance of one month was made for late vaccinations,
so that at the time of interview, if a child was due for a vaccination in
the previous month and had not received it, that dose was not included in
the calculation of vaccination status. Adult respondents were asked whether
they had been vaccinated for influenza in the last 12 months, and for pneumococcal
disease in the last five years.

Vaccination
coverage estimates from the National Health Survey for Indigenous versus
non-Indigenous children

Coverage estimates from the
National Health Survey for Indigenous and non-Indigenous children were provided
by the ABS and are presented here for children aged 2–6 years in Table 12.
Estimated coverage at six years was considerably lower for both Indigenous
and non-Indigenous children than recorded on the ACIR for one and two year
olds.

For Aboriginal and Torres
Strait Islander children in non-remote areas, estimated coverage ranged from
85 per cent for one or more doses of MMR to 50 per cent for three or more
doses of Hib. Coverage for non-Indigenous children was statistically significantly
higher for DTP, OPV and Hib, and almost so for MMR. Coverage for non-Indigenous
children ranged from 94 per cent for one or more doses of MMR to 67 per cent
for four or more doses of Hib. The vaccine with the largest difference in
coverage between Indigenous and non-Indigenous children was Hib (17%), while
the smallest difference was for MMR (9%). Parents of Indigenous children
were less likely to have referred to immunisation cards or records (56%,
95% CI 43–69%) than parents of non-Indigenous children (80%, CI 77–83%).
The proportion of parents of Aboriginal and Torres Strait Islander children
who reported they either did not know whether their child was vaccinated,
or did not know how many doses they had received, ranged from six per cent
for MMR to 23 per cent for Hib. For parents of non-Indigenous children, the
proportions ranged from six per cent for OPV to nine per cent for Hib.

Vaccination
coverage estimates from the National Health Survey for Indigenous versus
non-Indigenous adults

Coverage estimates for influenza
and pneumococcal vaccines in age groups relevant for the fully funded vaccine
programs among Indigenous and non-Indigenous adults are shown in Table 13.
Pneumococcal vaccine coverage was significantly higher in Aboriginal and
Torres Strait Islander adults at 50–64 years (Indigenous 20%, non-Indigenous
3%) and 65 years and over (Indigenous 47%, non-Indigenous 28%). Influenza
vaccine coverage was significantly higher in Aboriginal and Torres Strait
Islander adults at 50–64 years (Indigenous 47%, non-Indigenous 26%) but not
when those aged 65 years and over were added (50+ years; Indigenous 51%,
non-Indigenous 47%).

Data on remoteness were available
for Aboriginal and Torres Strait Islander people only. For those aged 50
years and over, coverage was substantially higher in remote areas than in
non-remote areas for both influenza vaccine (75% vs 45%) and pneumococcal
vaccine (48% vs 19%).59

Table 13.
Vaccination coverage estimates from the National Health Survey for Indigenous
and non-Indigenous adults, by age

Vaccine

Indigenous
status

50–64
years

65+
years

Total
50+ years

Influenza*

Indigenous

47
(38–56)

71
(50–92)

51
(43–59)

Non-Indigenous

26
(24–28)

75
(74–76)

47
(46–48)

Pneumococcal†

Indigenous

20
(15–25)

47
(29–65)

25
(19–31)

Non-Indigenous

3 (2–4)

28
(26–30)

14
(13–15)

Source:
Unpublished data from the National Health Survey, provided by Australian
Bureau of Statistics.

* Vaccinated
in the last 12 months.

† Vaccinated
in the last five years.

Other data

Previously published national
data on immunisation coverage in Aboriginal and Torres Strait Islander people
is largely limited to the 1996 'Wronski Report'.60 This report
estimated levels of immunisation coverage in Aboriginal and Torres Strait
Islander children by surveying community controlled Aboriginal and Torres
Strait Islander Health Services and regional health bodies. Of 25 services
providing data, estimated coverage in two years old and five years old children
varied from 14 per cent to 100 per cent, with generally higher coverage in
non-urban areas compared to urban areas.60 A more recent study13 has
estimated national immunisation coverage using Australian Childhood Immunisation
Register records with receipt of PedvaxHIB immunisation as a proxy for Aboriginal
and Torres Strait Islander status. Using this method, coverage in Aboriginal
and Torres Strait Islanders at 12 months (72%–76%) and 24 months (64%–73%)
was considerably lower than in others (90%–94% and 81%–88% respectively).
As in the National Health Survey, coverage was significantly lower in children
residing in 'accessible' compared to 'remote' areas.13

Other data on immunisation
coverage in Aboriginal and Torres Strait Islander children has come largely
from specific areas in particular States. Surveys of immunisation providers' records
have reported rates from 36 per cent fully vaccinated for children up to
11 years of age on the North Coast of New South Wales in 199261 to
73 per cent by two years of age in Central Australia in 1985.62 In
Far North Queensland in 1996, coverage was estimated to be less than 42 per
cent by two years of age.63 Studies examining computerised immunisation
registers in the Northern Territory have reported uptake rates of above 95
per cent for most vaccines at two years of age in remote communities in 1993.64 Overall
coverage, measured as fully immunised at six years of age, was estimated
as 77 per cent for the whole Northern Territory in 1996.65 Studies
have consistently reported significantly higher coverage rates in remote
communities compared to urban areas in Northern Australia63,65,66 but
the reverse was found in Northern New South Wales.61

Comment

Immunisation coverage from
the National Health Survey is generally lower than that from the ACIR and
the NHS figures show a larger discrepancy between rates in Indigenous and
non-Indigenous children. There are several possible reasons for this. First,
the NHS coverage estimates only include children whose vaccinated status
could be determined. The data above also show that parents of Aboriginal
and Torres Strait Islander children were less likely to have written records
to refer to. They were therefore more likely to report that they did not
know the status of their child and therefore not be recorded as vaccinated.
Under-reporting of vaccination to the ACIR also occurs, but it has been estimated
at 2.5 per cent for the general population,14 considerably lower
than the 6–9 per cent of non-Indigenous children with unknown vaccination
status in the NHS, and 8–23 per cent for Indigenous children. NHS estimates
did not include children from remote areas. Given that coverage has frequently
been shown to be higher in Indigenous populations in remote compared to urban
areas,59,66 this may also have contributed to underestimating
Indigenous coverage.

For those children who are
recorded as Indigenous on the ACIR, coverage is similar to that in the general
population by two years of age. Coverage for DTP and OPV were lower than
in the general population at 12 months of age, but there was little difference
by two years. As there are no doses of DTP or OPV recommended between one
and two years of age, this indicates that the main reason for lower coverage
at 12 months for those recorded as Indigenous on the ACIR is delayed receipt
of the vaccines due at 0–6 months.

Approximately 65 per cent
of the estimated number of Aboriginal and Torres Strait Islander children
born between June 2001 and December 2002 are recorded as Indigenous on the
ACIR. To the extent that data completeness is an indicator of access to health
care then these children may be more likely to be vaccinated than those whose
status has not been recorded. It is likely, therefore, that the ACIR and
NHS respectively provide an upper and lower limit of the coverage in Aboriginal
and Torres Strait Islander children and the difference between Indigenous
and non-Indigenous children. Improved reporting of Indigenous status on the
ACIR in future may enable the monitoring of trends over time and geographical
differences. Ideally, any future NHS examining immunisation status in an
enhanced sample of Aboriginal and Torres Strait Islander children should
seek to map this to the ACIR, for identification of both Indigenous and immunisation
status.

In adults, coverage was higher
for Aboriginal and Torres Strait Islanders for pneumococcal vaccine in those
aged 50 years and over and for influenza vaccine at 50–64 years. This higher
coverage is probably attributable to the provision of free vaccine through
the National Indigenous Pneumococcal and Influenza Immunisation program.
There was no significant difference in influenza vaccine coverage at 65 years
and over, where vaccine is recommended and provided free to the general population.

Discussion

This report gives, for the
first time, detailed data on VPDs and vaccine coverage in Aboriginal and
Torres Strait Islander people and compares these data with those for the
population not recorded as Indigenous. These data add to the more general
data on communicable disease and health in the report(s) of the Australian
Institute of Health and Welfare and the Australian Bureau of Statistics.2 They
have direct implications for prevention, both in considering new or expanded
vaccine programs and in improving the population coverage of existing programs.

With the exception of hepatitis
A, all VPDs considered in detail in the report are currently targeted by
population-wide programs. Each VPD highlights different issues for consideration.
For childhood programs, Hib disease, pertussis and measles provide interesting
contrasts. In the case of Hib disease, great progress has been made in preventing
this life-threatening infection across the population, but the residual disease
burden, though much diminished, is falling disproportionately on Aboriginal
and Torres Strait Islander people. More information is needed on the reasons
for this, as vaccination coverage data from the NHS and ACIR do not show
a consistent picture. In contrast, ACIR data show little difference in younger
children aged one and two years. For pertussis, although there is little
difference in incidence rates across all ages, this is not the case in the
youngest children. Both Hib disease and pertussis can affect very young infants
below six months of age and the data suggesting delayed immunisation in Aboriginal
and Torres Strait Islander children may be particularly relevant here. In
the case of measles, where early receipt of vaccine is not so critical and
a recent nationwide campaign was delivered in schools, good control of equivalent
degree is evident for Indigenous and non-Indigenous people.

Different issues are highlighted
by examination of the data on disease incidence and vaccine coverage for
hepatitis B, meningococcal disease, influenza and pneumococcal disease, all
with established programs targeting a wider age group. In the case of hepatitis
B, Aboriginal and Torres Strait Islander infants have been included in targeted
programs since the late 1980s and the oldest will now be more than 15 years
of age. In the Northern Territory, where the program was universal rather
than targeted, high coverage may have been more successful than in regions
with targeted programs. Certainly the data showing high incidence and significant
differential incidence in the 5–14 years old age group suggest that there
may have been sub-optimal coverage. Indeed, relatively high rates of hepatitis
B notification for Aboriginal and Torres Strait Islander young people suggest
that a program targeting this age group should be considered. A national
program of meningococcal C conjugate vaccination has been in place since
early 2003. Available notification data indicate that the significantly higher
rates of invasive meningococcal disease in Aboriginal and Torres Strait Islander
people are primarily in children under two years and are mostly type B, for
which no licensed vaccine is available. It will be important to have more
complete serogroup-specific data available for Aboriginal and Torres Strait
Islander cases in the future.

High morbidity from influenza
and pneumococcal disease in Aboriginal and Torres Strait Islander people
has been targeted by a funded vaccine program for adults over 50 years since
1999. Children under two years of age have been targeted for a funded program
of conjugate pneumococcal vaccine since 2001. The data presented here show
that the incidence of these diseases remains high and, in the adult program,
there is significant scope for increasing vaccine coverage. This is particularly
the case in adults aged 50–64 years where coverage, although higher than
in non-Indigenous adults for whom there is no funded program, remains low.
There is also a high disease burden from influenza and pneumococcal disease
in 25–49 years old Aboriginal and Torres Strait Islander adults, potentially
justifying expansion of the program to all Aboriginal and Torres Strait Islander
adults in this age group. However, it will be important to first identify
means of achieving higher coverage in the young adult population.

In the last category is hepatitis
A, where no national vaccine program exists for any population group. In
north Queensland, hepatitis A has been targeted by a vaccination program
for Aboriginal and Torres Strait Islander children under five years of age
with dramatic falls in disease incidence extending to other age groups and
the non-Indigenous population.31 This experience, and similar
experiences with hepatitis A programs in Indigenous communities in the USA,
suggest that hepatitis A should also be strongly considered for a national
program, at least in high incidence areas, as is done in the USA.

In summary, the data in this
report reveal some important areas where increased attention is justified
and consideration of expanded programs and mechanisms of enhancing existing
programs should be expedited. Limitations of the available data relate both
to VPD and vaccine coverage data, though the issues in each differ. For VPD
data, incomplete identification of Aboriginal and Torres Strait Islander
status is a problem, tending to underestimate disease burden. However, even
the available data indicate a substantially higher burden from VPDs in almost
all instances, with the limitation that information about Aboriginal and
Torres Strait Islander people living in the southern parts of the country
and in urban areas is less complete. For vaccine coverage, there is the possibility
of overestimating completeness of coverage through the ACIR, depending on
the characteristics of children identified as Indigenous in it. On the other
hand, the range of years and small sample sizes for individual years significantly
limits the interpretation of data from the National Health Survey, as does
lack of availability of records. Expansion of the ACIR to include other age
groups, should this occur in the future, may be able to address this problem.

31. Hanna JN,
Hills SL, Humphreys JL. The impact of hepatitis A vaccination of Indigenous
children on the incidence of hepatitis A in North Queensland. Communicable
Diseases Control Conference; 2003 31 March–1 April; Canberra.

* Notifications
(New South Wales, Northern Territory, South Australia and Western Australia
only) where the date of onset was between 1 January 2000 and 31 December
2002; hospitalisations (all states) where the month of separation was between
1 July 1999 and 30 June 2002; deaths (Queensland, Northern Territory, South
Australia and Western Australia) where the date of death was recorded between
1 January 2000 and 31 December 2002.

† See
results section for case definitions. For diseases not included in Section
3, case definitions are listed below.

‡ Average
annual rate per 100,000 population, age standardised to the ABS Australian
population estimates for 2001.1